Absorbent structure

ABSTRACT

An absorbent structure with a sequence of two layers includes at least one liquid absorption layer, a subsequent liquid storage layer with super absorbent polymer particles and super absorbent polymer fibers, and a subsequent liquid distribution layer. The layers are connected and form a sheet structure. The liquid storage layer has its super absorbent polymer extending from the liquid storage layer into the liquid distribution layer in order to generate a return suction effect for the liquid that has passed through the liquid absorption layer and liquid storage layer into the liquid distribution layer.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an absorbent structure including aliquid absorbent layer, a liquid storage layer and a liquid distributionlayer using cellulose fibers and preferably super absorbent polymerparticles, abbreviated as SAP particles. The super absorbent polymer canalso be provided in another form, for example, through a fiberstructure. Preferably, the absorbent structure is mostly made fromcellulose fibers.

2. Description of the Background Art

Air laid products using cellulose and super absorbent polymer particleshave been known for years and are used as a layer material in hygieneproducts, medical products and industrial products.

For example, WO00/74620 describes a uniform absorbent structure usingair laid material, cellulose fibers and binders, preferably based onlatex and/or polyolefin containing bi-component fibers, wherein thestructure includes a liquid absorbent layer, a liquid storage layer anda liquid distribution layer with a respective pore structure, whereinthe mean pore size of each layer decreases with a gradient in adirection from the absorbent layer to the distribution layer.

In the products known so far, a capillary effect is used fortransporting liquids in which the capillary effect is generated througha selection of the pore structure in order to move the liquid in acontrolled manner into a storage position and to reduce undesirable backwetting effects which can occur through run out of liquid from a liquidabsorbent layer into a liquid distribution layer and beyond, for exampleonto the skin of a carrier of a hygiene product.

Therefore, it is desirable to have a product available through whichback wetting effects of this type can be prevented and simultaneously avery efficient use of the absorption power of super absorbent componentsis provided.

SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to provide a productand a method and a device for producing the product which prevents backwetting while providing an optimal use of an absorption power of superabsorbent components.

The object is achieved with an absorbent structure, a method forproducing on absorbent structure and a device according to theindependent claims. Preferred embodiments are defined in the dependentclaims. One or plural features from these embodiments, however, are alsolinkable with other features from the subsequent description to formadditional embodiments and are not limited to the respectively claimedembodiment. Also the respectively proposed features in particular alsoof the respective dependent claims are only a first approach, whereinone or plural of the features can be supplemented and/or replaced withthe subsequent features.

An absorbent structure is proposed with a sequence of two layersincluding at least one liquid absorbent layer, a subsequent liquidstorage layer with super absorbent polymer SAP, preferably configured inthe form of SAP particles and/or SAP fibers and a subsequent liquiddistribution layer, wherein the layers are connected and form a layerstructure. Thus, at least the liquid storage layer and the liquiddistribution layer at least respectively include an air laid material asmain component, preferably an air laid layer, which includes cellulosefibers. At least the liquid storage layer includes SAP particles. Thesuper absorbent polymer of the liquid storage layer, preferably providedin the form of SAP particles and/or SAP fibers, extends partially intothe liquid distribution layer and thus comes into direct contact withthe liquid which is distributed in the liquid distribution layer of theproduct. The super absorbent polymer causes a back suction effect forthe liquid which has entered through the liquid absorption layer and theliquid storage layer into the liquid distribution layer.

According to another embodiment, it is provided that the liquidabsorption layer includes an air laid material. Preferably this layer atleast to a major portion is made from cellulose fiber. It canfurthermore be provided that the liquid absorption layer includesthermoplastic fibers. These fibers can be for example gluing fibers. Forexample, bico fibers, in particular core-jacket-fibers can be used inwhich the jacket has a lower melting point than the core. Anotherconfiguration provides that the liquid absorbent layer includes avoluminous fleece made from thermoplastic fibers. The voluminous fleeceaccording to one embodiment is a carded fleece. One embodiment providesthat the voluminous fleece is a hot air solidified fleece made fromthermoplastic fibers. According to one embodiment, staple fibers arebeing used. The voluminous fleece can include fibers made frompolyester, polypropylene, viscose and/or polyethylene. The voluminousfleece according to one embodiment can have a weight per unit area of 30to 90 g/m². An embodiment for a usable material is Paratherm Loft 142/25made by TWB Corporation.

Preferably, all layers of the absorbent structure are produced in anin-line process. Furthermore, there is the option that at least onelayer of the absorbent structure is at least prefabricated and suppliedto the manufacturing process as an intermediary product. Thus, theintermediary product can be rolled onto a winder and subsequently rolledoff again at the production line and supplied to the process. Oneembodiment provides that, for example, a layer is provided which is usedas a liquid absorption layer in the subsequent absorbent structure.Another embodiment provides that, for example, a prefabricated layer isprovided which functions as a liquid distribution layer in thesubsequent finished absorbent structure. Another embodiment providesthat at least one of the layers can also be configured with multiplelayers. For example, the liquid distribution layer can be connected withanother layer, preferably with a smaller pore size than the fiber layerprovided with the liquid distribution layer, for example a tissue layer.A preferred embodiment provides that the tissue layer is arrangeddirectly adjacent to the air laid layer and connected with the air laidlayer which forms the liquid distribution layer. The tissue can supportliquid distribution through having a smaller pore size than the air laidlayer. The smaller pore size also causes a higher capillary force. Thetissue for example can form an outside of the absorbent structure. Avoluminous fleece made from thermoplastic fibers, preferably staplefibers can for example form the other outside of the absorbentstructure.

Using a thermoplastic material in the liquid absorption layerfacilitates for example an improvement of the recurring wetability.Thermoplastic fibers prevent absorption of liquid in the liquidabsorption layer. Instead, the liquid is passed on to the liquid storagelayer. Therein the liquid is stored, wherein a portion of the liquid canalso get into the liquid distribution layer. From there, the liquid isdistributed for example along the distribution layer before it is suckedback into the liquid storage layer.

In case the suction force of a super absorbent material (SAP) issignificantly higher than a capillary force of respective layers of theproduct, it is feasible to transport liquid, which moves through thegradient of the capillary force from the liquid absorbent layer throughthe liquid storage layer into the liquid distribution layer and which isdistributed therein, from the liquid distribution layer into the liquidstorage layer and to store it there in the super absorbent materials.

One embodiment provides that the liquid storage layer includes opencavities and/or portions with large pores in its interior. The portionscan be used so that the super absorbent material expands into them afterthe receiving the liquid when the super absorbent material swells. Thecavities can used, for example, so that super absorbent materialdistributes in this direction, in particular during the productionprocess of the absorbent structure. For example, this can be providedthrough vibrating during the production process.

According to one embodiment, the absorbent structure includes a gradientwith respect to a pore structure which supports an outflow from theliquid absorbent layer towards the liquid distribution layer. Thegradient structure can extend within one layer but can also extend overplural layers. The gradient can preferably cause an increase of thecapillary force. A gradient is adjustable, for example, through the formof deposition of the cellulose fibers through additional compressionand/or reduction of the pores through additional means, for example,supplying liquid or binder which reduces the size of the pores orpartially plugs the pores. This can be on provided for example throughlatex wetting.

A pore size can be determined through image generating methods. Thus,for example, a cut is performed along a longitudinal surface of a layerstructure. Therefore, the material is, for example, cooled down so thatit can be cut without destroying the structures within the layer duringcutting. The cut is then photographed and evaluated through imageprocessing methods. A gradient is generated, for example, in that thepore size decreases transversally to a layer. Thus, the number of poresin the section is measured and their respective size is determined.Through forming a ratio of both sizes, namely the number of pores andthe sum of their respective size, a mean pore size for this layer can bedetermined. A cross-section to be examined should be at least 20 mm×20mm.

A preferred method for producing a section is using a cryoscopicfracture or cut with an extremely sharp blade, preferably through amicrotome. A section surface thus produced can subsequently beevaluated, for example, through taking a picture of the cut surface andsubsequently preferably automatic counting. There is also the option togenerate a scanning electron microscope image which is subsequentlyevaluated. This is performed, for example, by the Saxonian Institute forTextile Research, STFI in Chemnitz, Germany in a standardized manner.

Besides forming a gradient along a layer, a gradient can also beprovided in a layer transversally thereto. The gradient can, forexample, be determined through a method as described supra.

A first gradient comparing the particular layers can, for example, alsobe accessed through an assessment of the respective cross-sectionperpendicular to the longitudinal extension of a layer. This gradient istherefore designated as total layer gradient. A second gradientcomparing the particular layers can for example be determined in thatthe uppermost and the lowest transversal layer of a respective layer areconsidered. These are, for example, compared with one another. From thisinformation can be derived whether a layer has a higher resistanceagainst liquid exit in upward direction or in downward direction. Bothlayers can also be respectively determined with respect to theirrespective mean pore size. Thus, a respective threshold value of a meanpore size of the layer is determined. For example, a mean can be formedagain from the two threshold values, wherein the mean is designated asthreshold gradient. It is preferable when the respective threshold valuegradient and the respective threshold value respectively increase viewedover a layer structure.

Another embodiment provides, for example, that the mean pore size in atransition from one layer to another layer respectively decreases fromthe liquid absorption layer to the liquid distribution layer.

The absorbent structure has the advantage that liquid which runs fromthe liquid absorption layer into the liquid storage layer during use ofthe absorbent structure is absorbed and preferably also distributedwhich prevents back wetting effects through liquid run out. Adistribution of liquid, however, is not only performed into alongitudinal direction within the liquid distribution layer. It hasrather become apparent that a back flow can be adjusted through acontrolled adjustment, arrangement and distribution of the SAP particlesand/or SAP fibers between the two layers, wherein the liquid is alreadyabsorbed through the SAP particles and/or the SAP fibers in the liquiddistribution layer and then moves back through the SAP particles and/orSAP fibers into the liquid storage layer. This mechanism can besupported for example through an adjustment of the porosity of the airlaid material used. According to one configuration, a material can beused herein as derived for example from WO 00/74620. A gradient of thistype with respect to density and/or porosity can for example also beused herein. In the structure described in WO 00/74620 including theliquid absorption layer, liquid storage layer and liquid distributionlayer besides the gravitation force only a capillary force is providedwhich is oriented from the liquid absorption layer to the liquiddistribution layer. Thus, in the structures described in WO 00/74620, abackflow of the liquid from the liquid distribution layer into theliquid storage layer is physically not possible. The technical teachingsthus proposed, however, lead to a facilitation of an embodiment of abackflow.

One embodiment provides that the SAP particles and/or SAP fibersprotrude in an uneven manner into the liquid distribution layer from theliquid storage layer. Another embodiment provides that there areportions into which no SAP particle and/or SAP fiber protrudes into theliquid distribution layer from the liquid storage layer while inadjacent portions at least the majority of the SAP particles and/or SAPfibers, this means at least 50% protrude into the liquid distributionlayer from the liquid storage layer. Another configuration provides thatthere are portions within which fewer SAP particles and/or SAP fibersprotrude into the liquid distribution layer from the liquid storagelayer compared to adjacent portions, in particular compared to portionsin which at least the majority of the SAP particles and/or fibersprotrude into the liquid distribution layer from the liquid storagelayer.

It is preferred when the absorbent structure includes SAP particlesand/or SAP fibers which at least by a third of a longitudinal extensionprotrude into the liquid storage layer. A protrusion of the longitudinalextension can, for example, depend on which thicknesses the variouslayers have. It is preferred when the SAP particles and/or SAP fibersprotrude at least far enough into the liquid distribution layer so thatthey protrude by 10%, preferably 25% of a thickness of the liquiddistribution layer into the liquid distribution layer.

In a SAP fiber, the length is determined in that its extension frombeginning to end is measured as a shortest distance in the structure.This also applies for wound SAP fibers. SAP fibers can be usedapproximately straight and also in a wound structure.

One embodiment provides that in an absorbing structure more than 20%,preferably more than 40% of the SAP particles and/or SAP fibers arrangedin the liquid storage layer protrude into the liquid distribution layer.Another embodiment provides that more than 40% but less than 70% of theSAP particles and/or SAP fibers arranged in the liquid storage layerprotrude into the liquid distribution layer.

It is furthermore preferred for an absorbent structure that the SAPparticles and/or SAP fibers protruding into the liquid distributionlayer after liquid absorption have grown more in the liquid storagelayer than in the liquid distribution layer. Thus, for example, theswelling capability of an SAP particle or an SAP fiber can be configuredso that it extends in a direction of least resistance. When the liquidstorage layer has less resistance, for example, through less density, astructure with more open pores, less bonding adhesion of the fibersamongst one another and/or through other means which can cause aresistance against distribution placement in a portion of the liquidstorage layer and preferably the fibers, a swelling SAP particles or anSAP fiber can, for example, not only swell preferably in the liquidstorage layer. Thus, for example, a movement of the swelling SAPparticle or of the fiber can be performed back into the liquid storagelayer. According to a preferred embodiment it is provided that SAPparticles and/or SAP fibers protruding into the liquid storage layerafter liquid absorption have at least partially pulled back into theliquid distribution layer.

The super absorbent material, for example, provided in the form of theSAP particles and/or SAP fibers described supra is swell-capable andtypically transitions into a gel type condition. Thus, the fibers cannotonly store water. Rather, the SAP particles in an arrangement asdescribed supra in the layer structure are capable of generating asuction flow and thus can be used for example as drainage material forthe liquid distribution layer.

Chemically speaking, SAP can be co-polymers which include, for example,acrylic acid and sodium acrylate, wherein the ratio of the two monomersrelative to one another can vary. Additionally, for example, crosslinkers are added during polymerization, wherein the cross linkersconnect the formed long chain polymers at some locations with oneanother through chemical bridges. The properties of the polymer can beadjusted as a function of the degree of cross linking. One configurationprovides, for example, that two different SAP materials, for example,two different SAP particles, two different SAP fibers and/or SAPparticles and SAP fibers that differ from one another and haveproperties that differ from one another are being used. Thus, thedifference can be in the liquid absorption capability, the speed ofliquid absorption, the swelling itself during liquid absorption, a timedelay until the liquid absorption starts, a liquid absorption rate oranother parameter. Various SAP materials can be arranged in a mixedmanner and also separate from one another in various portions. Thedifferent portions cannot only be arranged in machine-direction andcross-direction of a processing with respect to an air laid productiondevice. Rather also an arrangement along a thickness of the material candiffer, thus, in particular, different portions can be configured.

For example, SAP materials can be used as they can be derived from EP0810 886, in particular also from the prior art recited therein which isincorporated in its entirety by this reference. One embodiment provides,for example, that SAP particles include a coating. The coating, forexample, can only dissolve in the presence of a liquid in order tofacilitate reception of the liquid by the SAP particle in the firstplace. This is an option how, for example, a time delay of absorptionand preferably sucking back liquid in the liquid distribution into theliquid storage system can be adjusted. For example, a first SAP materialcan be arranged in the liquid storage layer, wherein the first SAPmaterial is not coated, and a second SAP material can be arranged whichis coated. Through the liquid contact initially the first SAP materialbinds the liquid. Overflowing liquid enters the liquid distributionlayer, wherein the second SAP material is only activated with a timedelay after the liquid flows by or contacts the same. Thus, the secondSAP material is configured in particular to act as drainage and to suckback liquid in order to be able to establish a back flow into the liquidstorage layer. Thus, it can be provided that the second SAP materialessentially protrudes into the liquid storage layer, the first material,however, hardly protrudes in the liquid storage layer or does notprotrude in the liquid storage layer at all. This is adjusted, forexample, through the layer structure and also through the subsequentpressure onto the generated layer structure.

Furthermore SAP material can be used as can be derived respectively fromDE 10 2004 015 686 A1, DE 698 217 94, and/or DE 10 2004 005 417 A1respectively, in particular with reference to the configuration and thestructure, the geometry of the super absorbent polymer and also thematerials and manufacturing methods used. Reference is made to theseprinted documents in an exemplary manner in the context of thedisclosure. Another embodiment provides that the SAP particles areprovided granulate shaped and that they can also have another geometry;for example they can be provided in the form of fibers or in otherforms. Fibers comprising a certain amount of super absorber can bederived from DE 10 232 078 A1 and also DE 10 251 137 A1. Also thesedocuments are incorporated in their entirety by this reference.

Another embodiment provides that the properties of the SAP are adjustedin a controlled manner, preferably as a function of the liquid to beabsorbed, but also as a function of the absorbing product and therespectively prevailing conditions for the SAP. There is the approachAAP which stands for absorption against pressure in order to demonstratehow SAP can absorb in spite of pressure. Thus, there is theWSP-EDANA-Method WSP 242.2 (05). Furthermore, the SAP can be describedthrough the so called free swell capacity according to the method WSP240.2 (05). There is also the possibility to consider the centrifugeretention capacity (CRC) WSP 241.2 (05). A preferred embodiment providesto describe a characterization of the SAP's based on the ratio of“absorption against pressure” to “free swell capacity”. According to oneconfiguration, an SAP is used with a CRC-value of 30-35 g/g and an AAPvalue depending on the cross link value of 18-24 g/g.

Preferably the swelling pressure of the SAP for sucking up liquid fromthe liquid distribution layer into the liquid storage layer is used.Thus, the SAP includes, for example, a swelling pressure in the amountof 6-8 bar, accordingly approximately 80-90 meters water column. Thisvalue is much higher compared to a capillary force which can develop forSAP with a water column of less than 1 meter. The swelling pressure canthus be used as a vertical force in order to retrieve the liquid fromthe liquid distribution layer into the liquid storage layer.

In one embodiment, the absorbent structure is configured as a layerstructure, wherein the layer structure includes at least one boundaryarea and wherein the layer structure includes cavities within the liquiddistribution layer and/or the liquid storage layer and/or the liquidabsorption layer and/or a boundary area between the liquid distributionlayer and the liquid storage layer and/or the liquid absorption layer.

These cavities can be generated, for example, when producing theabsorbent structure. For example, in that the layers are connected whichforms the layer structure and wherein during the binding process astretching of the layer structure is performed that is at least orientedin machine direction. The air laid layers are connected and compressedthrough thermal bonding, using binders and using calendering. Throughthis bonding process, the layer structure thus obtained can relax again,wherein the cavities within the air laid layers or at its boundarysurfaces also relax and are visible in the absorbent structure aspreferably irregular cavities in which preferably no cellulose fibersand preferably also no SAP particles and/or SAP particles are arranged.

Preferably, these cavities are configured larger in the liquid storagelayer than in the liquid absorption layer and/or in the liquiddistribution layer.

Another embodiment provides that the absorbent structure is configuredso that at least a portion of the cellulose fibers of the air laidlayers of the liquid distribution layer and/or of the liquid storagelayer and/or of the liquid absorption layer are mixed with one anotherin the liquid boundary area.

Preferably, the air laid layers of the liquid distribution layer and/orof the liquid absorption layer transition into one another within theboundary area.

One embodiment provides that the air laid layers of the liquiddistribution layer and/or the liquid storage layer and/or the liquidabsorption layer within the layer structure are not differentiable fromone another. Preferably, identical or similar cellulose fibers are beingused. For example, the fibers are deposited at separate stations. Afterstorage, however, two layers are not differentiatable from one anotheranymore based on a sharp phase boundary. Rather, the layers transitioninto one another or not more than two different layers are identifiablein a cross sectional view.

The absorbent structure can be configured so that the liquiddistribution layer has a first and second surface, wherein the firstsurface is in contact with the liquid storage layer and wherein theliquid distribution layer is compressed to a greater extent at itssecond surface than at its first surface.

It has proven advantageous that the liquid storage layer has a higherdensity than the liquid distribution layer and/or the liquid absorptionlayer. A density computation is thus performed for the entire density ofthe layer; this means all components of a layer are included. Thus, thelayer is measured and density is computed with reference to thedimension of the layer. Thus, as a result a mean density can bedetermined which characterizes the layer.

One embodiment provides that the SAP particles and/or the SAP fibersprotrude from the liquid storage layer into the liquid distributionlayer. It has become apparent that through the capillary force actingwithin the layer structure and within the particular air laid layersliquid flows initially from the liquid absorption layer to the liquiddistribution layer. Through the SAP particles and/or SAP fibersprotruding from the liquid storage layer into the liquid distributionlayer a suction effect is generated which lets liquid flow from theliquid distribution layer back into the liquid storage layer. Accordingto an embodiment it is provided that for a first liquid dispensing ontothe liquid absorption layer the suction effect which is caused by theSAP particles and/or the SAP fibers is provided with a time delayrelative to the suction effect through capillary effects. According toanother embodiment, it is provided that for multiple liquid applicationsthere is a superposition of transport processes for the liquid, whereinpreferably the transportation through the capillary forces is typicallyperformed quicker than the back transportation of liquid from the liquiddistribution layer into the liquid storage layer through the superabsorbent materials.

It has also proven advantageous to configure an absorbent structure sothat at least one liquid absorption layer is provided and a liquidstorage layer configured as a layer with plural layers, preferably alayer with two layers. For example, the liquid storage layer can beformed from at least:

-   -   one layer, including an air laid layer, preferably including        cellulose fibers and SAP particles and/or SAP fibers and at        least one additional layer including SAP particles or    -   two layers respectively including an air laid layer, preferably        including cellulose fibers and SAP particles and/or SAP fibers.

Introducing super absorbent polymers preferably in the form of SAPparticles and/or SAP fibers in another layer of the absorbent structurefacilitates for example that the absorbent structure can take over thefunction of a liquid storage layer and also of a liquid distributionlayer. The layer according to one embodiment preferably includes thehighest density within the liquid storage layer or the liquiddistribution layer of the layer structure and thus has very good liquiddistribution properties. Furthermore, the layer can help to improveexpansion properties of the layer structure for example also withrespect to an elastic property. Another advantage is that the SAPparticles and/or SAP fibers within the layer can expand very well andsufficient space is available for swelling which improves the absorptioncapabilities of the layer structure. Thus, an additional layerfacilitates embedding a higher portion of SAP particles and/or SAPfibers. Thus, a product of this type can in particular fulfill therequirements of incontinence products.

Thus, the respective layers can include identical or different types ofcellulose fibers and/or SAP particles and/or SAP fibers. This way thereceiving properties of the particular layers of the layer structure canbe adjusted in a defined manner.

For example, in one layer, highly permeable SAP particles and/or SAPfibers can be used which together with SAP particles and/or SAP fibersin another layer cause a two stage absorption and storage effect. Forexample, in one layer which is oriented towards the liquid absorptionlayer, SAP particles and/or SAP fibers with high absorption capabilitycan be provided and in another layer semi permeable SAP particle and/orSAP fibers can be provided. Thus, a buffer function in another layer canbe generated which is advantageous in particular when a liquid isapplied several times.

In another embodiment the liquid absorption layer includes at leastcellulose fibers and bi component fibers, wherein the liquid storagelayer includes at least cellulose fibers and SAP particles and/or SAPfibers.

One embodiment provides that the bi component fibers have a core jacketstructure. It is also provided that the bi component fibers include atleast one PET. Advantageously, the bi component fibers includes at leastone polyethylene preferably a LDPE or a LLDPE. In a bi component fiberwith a core jacket structure, a polymer is provided in the core thatincludes PET or a poly propylene and a jacket is provided that includespolyethylene. The bi component fibers are preferably used as bondingfibers. Through heating the fibers are at least softened enough, so thatthey form a gluey surface at which cellulose fibers and other componentsof the layer but also components of adjacent layers are firmly attachedduring cooling. According to one embodiment cellulose bonding fibers canbe used as they are derived from DE69808061 which is incorporated in itsentirely by this reference.

Another embodiment provides that at least cellulose fibers and bicomponent fibers are provided in the liquid absorption layer. The liquidabsorption layer includes at least cellulose fibers and SAP particlesand/or SAP fibers. The liquid distribution layer in this embodimentmostly includes cellulose fibers and a bonding agent layer is providedpreferably a latex layer.

The particular layers of the absorbing structure can include:

-   -   respectively the same type of cellulose fibers,    -   respectively different types of cellulose fibers,    -   mixtures thereof,    -   chemically and/or physically treated cellulose fibers,    -   untreated cellulose fibers,    -   mixtures of treated and untreated cellulose fibers,    -   synthetic fibers by themselves, or mixed with cellulose fibers        in treated or untreated form, and    -   fibers with mineral origin by themselves or mixed with synthetic        and/or cellulose fibers.

Particular fibers can also include cellulose fibers exclusively. Aparticular layer can thus be configured as liquid distribution layer orliquid storage layer or liquid absorption layer within the layerstructure of the absorbent structure. A particular layer can also beconfigured as a layer in a multi layer liquid distribution layer orliquid storage layer or liquid absorption layer.

The term “cellulose fibers” in the context of the disclosure is notgiven a limited interpretation. Any types of natural fibers are useablewhich are capable or rendered capable through a chemical or physicaltreatment to absorb liquids and to preferably also bond liquids. Througha treatment of this type also synthetic fibers and fibers with mineralorigin can be processed.

Chemical treatments can be for example the following:

-   -   washing processes,    -   extraction processes,    -   bleaching processes,    -   dying processes,    -   fibrillation processes using solvents,    -   surface treatment preferably for hydrophilization, increase of        strength or elasticity for example through spraying, dipping,        washing and similar.

A physical treatment can be performed through:

-   -   particulation and fibrillation, for example, cutting, milling,        breaking down into fibers,    -   classing, for example, wind sifting.

It has proven useful that the liquid absorption layer includes an airlaid layer which essentially includes chemically or physically nontreated cellulose fibers. According to another embodiment, the cellulosefibers of the liquid storage layer are not treated chemically and/orphysically. Another embodiment provides that the liquid absorption layeris configured as a cellulose free absorption layer or as an absorptionlayer that only includes a small amount of cellulose fiber and isconfigured as an air laid layer which, for example, includesthermoplastic fibers, such as staple fibers and the liquid distributionlayer includes an air laid layer, which essentially includes chemicallyand/or physically treated cellulose fibers. By using thermoplasticfibers as major fiber component of absorption layer, a rewetting withliquids and further conduction into the liquid storage layer can beimproved. Thus, in adaptation to an application, the fibers of theliquid absorption layer can be configured accordingly, for example, in ahydrophobic manner.

Particularly preferred cellulose fibers such as southern pine pulp typesby Koch Cellulose LLC are produced through a pulping process and ableaching process and have been finished. The fibers have an averagefiber length of 2.7 mm, a density of 0.9 g/cm³, a tensile strength of414 kPa, a humidity of 8%, a defibulatable portion of over 99.5%, aspecific absorption capability of 1.5 s/g.

These fibers due to their treatment are particularly suited for use inouter layers of the absorbent structure, such as the liquid storagelayer and the liquid distribution layer. Depending on the type offibrillation process for the fibers and the bleaching process, definedproperty combinations are achievable in the cellulose fibers.

It is provided that the chemical and/or physical treatment of thecellulose fibers of the air laid layer of the liquid absorption layerdiffers from the chemical and/or physical treatment of the cellulosefibers of the air laid layer of the liquid distribution layer.

In the liquid storage layer, preferably non treated fibers such assouthern pine are used. This has various reasons. The pulp losesabsorption capability through adding treatment agents in particularsurface treatment agents. In order to provide best possible absorptionin a liquid storage layer preferably a non treated pulp type is used.This pulp type can be best compressed in a process since the non treatedfibers have good adhesion.

In the outer layers of the absorbent structure which are preferablyformed by a liquid absorption layer and a liquid distribution layer, atreated cellulose pulp type is used due to the process in order toprevent adhesion at the devices used in a bonding process, for examplean embossing roller in the calender arrangement. The surface treatmentof the fibers furthermore reduces the adhesion between the fibers andthus improves compressibility of the fibers.

Cellulose fibers of Koch Cellulose LLC of the type GP 4821 are suitablefor application in an outer layer of an absorbent structure since theirvoluminous structure is adapted to the requirements of a calenderingprocess for compressing a layer structure.

According to one embodiment an absorbent structure is proposed, wherein:

-   -   the liquid absorption layer includes at least cellulose fibers        in a range between 60% by weight to 70% by weight and bi        component fibers in a range between 30% by weight to 40% by        weight with reference to the total weight of the liquid        absorption layer,    -   the liquid storage layer includes at least cellulose fibers and        SAP particles and/or SAP fibers in a range between 15% by weight        to 35% by weight with reference to the total weight of the        absorbent structure and wherein    -   the liquid distribution layer includes mostly cellulose fibers,        preferably 100% by weight with reference to their total weight.

Furthermore, the absorbent layer can include another binder layer, suchas a latex layer which is arranged on the liquid distribution layer.

A possible method for producing an absorbent structure can include thefollowing steps, wherein the sequence of the steps is variable:

-   -   depositing a first layer, preferably an air laid which        preferably includes at least cellulose fibers and bi component        fibers, and/or a highly voluminous fleece layer from        thermoplastic fibers for configuring a liquid absorption layer        which includes at least cellulose,    -   depositing a second air laid layer for configuring a liquid        storage layer which includes at least cellulose fibers and        SAP-particles and/or SAP fibers,    -   storing a third air laid layer for forming a liquid distribution        layer,    -   preferably applying the bonding agent layer,    -   preferably applying a bonding agent layer, preferably a latex        layer on one layer, preferably onto the layer structure thus        obtained,    -   preferably running the layer structure through heating devices        in order to bond the layer structure,    -   supplying at least one layer, preferably of the layer structure        to a calender including at least one smooth roller and an        opposite roller, preferably with protrusions which form a        calender gap,    -   compressing the at least one layer, preferably of the layer        structure of the calendar, wherein SAP particle and/or SAP        fibers protrude from the liquid storage layer into the liquid        distribution layer and form a liquid removing contact between        the liquid storage layer and the liquid distribution layer.

In particular, an absorbent structure is produced with a device of thistype as described supra and as will be described in more detail infra.

One embodiment provides initially that a liquid distribution layer suchas a pulp based distribution layer is placed by a first forming layer ona perforated band or pulled off from the perforated band. In asupplemental manner, in advance or subsequently, a tissue layer can beassociated. Building on the liquid distribution layer, a storage layerand eventually an absorption layer is arranged. Based on this concept, acalender is provided which includes a roller with the embossingprotrusions placed on the bottom so that the protrusions come in directcontact with the distribution layer or the tissue. A super absorbentmaterial from the storage layer can only be vibrated into the lowerdistribution layer through the process with gravity support. This layercan be fixated through a subsequent heat and/or pressure treatment oranother compression.

Another embodiment provides a method for producing an absorbentstructure including at least the following steps:

-   -   depositing a first air laid layer for configuring a liquid        storage layer which preferably includes at least cellulose        fibers and bi component fibers,    -   depositing a second air laid layer for configuring a liquid        storage layer which includes at least cellulose fibers and SAP        materials, preferably SAP particles and/or SAP fibers.    -   depositing a third air laid layer for configuring a liquid        distribution layer,    -   preferably applying a bonding agent layer, preferably a latex        layer onto the layer structure thus obtained,    -   preferably running the layer structure through a heating device        in order to bond the layer structure,    -   supplying the layer structure to a calender including at least        one first smoothing roller and an opposite roller preferably        with protrusions which form a calendering gap, and    -   compressing the layer structure in the calender gap, wherein SAP        particles and SAP fibers protrude from the liquid storage layer        into the liquid distribution layer and form a liquid removing        contact between the liquid storage layer and the liquid        distribution layer.

It is preferably provided that a SAP feed is provided between twosubsequent forming heads for producing a respective air laid layer. Thisway the protrusion of the SAP material into the adjacent layer can becontrolled in a particular manner. Thus, the liquid storage layer isformed by a forming head and the liquid distribution layer is formed bythe other forming head. This way there is also the option that anotherSAP material is used when producing the liquid storage layer which isdifferent from the SAP material which issued between the two otherlayers. However, there is also the option that other SAP materials areidentical.

The cuts can be performed in the recited sequence or in anothersequence.

One embodiment provides that a roller assembly is used for the methodthat has a set pressure through which a movement and a penetration ofthe SAP particles and/or SAP fibers deposited through the second airlaid formation device is provided into the adjacent cellulose fiberportions. In particular the SAP particles and/or SAP fibers can bepressed into an adjacent portion of another layer.

According to one embodiment the calender can include two smooth rollers.The calender can include also one smooth roller and one roller withembossing protrusions. Furthermore, there is the option that additionalheat is applied through a smooth roller which facilitates smoothing thesurface of the layer structure. In this way, an open porosity of thesurface of the material can be changed, in particular, it can bereduced. Another option for bonding can be derived from DE 102 18 259 A1which is incorporated in its entirety by this reference.

A connection of air laid layers among one another and also of fibers ina particular air laid layer can be provided through melting the bondingagent layer and/or the SAP particles and/or SAP fibers. Other bondingagents, such as latex that is sprayed on, are also useable. Gluingagents can also be used which are sprayed on through a nozzle system. Abonding agent application can be performed over the entire surface ornot over the entire surface, for example in the form of a regular orirregular pattern. A film can also be used which melts when the layersheat up so that it connects layers and/or fibers with one another.

One embodiment provides that the method includes an additional third airlaid layer on the second air laid layer for forming a liquid absorptionlayer wherein the third air laid layer includes at least cellulosefibers and bi component fibers. It is also provided that the followingsteps are performed in the desired sequence in the process:

-   -   applying a latex layer onto the liquid distribution layer,    -   running the layer structure thus obtained through a heating        device in order to activate the bi component fibers and to bond        the cellulose fibers,    -   feeding the layer structure to a calendar, and    -   compressing the layer structure in the calender gap.

It has proven advantageous that the absorbent structure is produced inline. This can remove the boundaries between the particular layers ofthe absorbent structure and can provide a mixing of the fibers ofrespective layers adjacent to one another.

Besides that also producing the absorbent structure by using separatemanufacturing steps is feasible, for example:

-   -   particular layers can be produced separately and bonded in a        subsequent bonding process to form a layer structure which forms        the absorbent structure,    -   prepregs or prelaminates and similar made from one or plural        layers can be provided which are subsequently configured with        other layers to form an absorbent structure.

Thus, the prepregs or prelaminates can include elements of one or pluralfunctional layers. A functional layer can be a liquid distribution layeror a liquid storage layer or a liquid absorption layer or elementsthereof such as a partial layer or a bonding agent layer or a layer withSAP particles and/or SAP fibers or a layer including bi componentfibers.

According to another embodiment of the invention, a device for producingan absorbent structure is proposed which includes at least the followingcomponents:

-   -   a perforated band for depositing air laid layers for forming a        layer structure,    -   a first air laid forming device from which at least cellulose        fibers are pullable that form an air laid layer,    -   a second air laid forming device from which at least cellulose        fibers and SAP particles and/or SAP fibers are depositable on        the air laid layer and preferably form a second air laid layer,    -   a depositing device for another layer,    -   an application device through which bonding agent, preferably a        latex layer is applicable,    -   a heating device in which bi component fibers and/or the bonding        agent are activatable,    -   a roller arrangement preferably a calender through which the        layer structure is compressible, and    -   a feed device for SAP particles and/or SAP fibers which are        supplied at least in a dosed manner and preferably also in a        position controlled manner and with partial penetration into the        cellulose fibers of an air laid layer, wherein the cellulose        fibers are adjacent to cellulose fibers of the second air laid        forming device.

The sequence of the components can deviate from the sequence recitedsupra. In particular, an absorbent structure is produced with a deviceof this type as described supra and as will be described in more detailinfra.

Furthermore preferably a device for providing bi component fibers isprovided wherein the bi component fibers can be deposited together withthe cellulose fibers on the perforated band and form an air laid layer.Also, a third air laid forming device through which at least cellulosefibers can be deposited on the perforated band can be integrated intothe production equipment. For example, the absorbent structure caninclude three air laid layers which are connected with one another.

One embodiment includes an improvement of the device for producing anabsorbent structure including at least the following:

-   -   a perforated band for depositing air laid layers for forming a        layer structure,    -   a first air laid layer forming device from which at least        cellulose fibers are pullable and preferably a device for        providing bi component fibers which are depositable together        with the cellulose fibers on the perforated band and which form        a first air laid layer,    -   a second air laid forming device through which at least        cellulose fibers and SAP particles and/or SAP fibers are        depositable on the first air laid layer and preferably form a        second air laid layer, wherein the second air laid forming        device adds SAP particles in a dosed and a position controlled        manner,    -   a third air laid forming device through which at least cell        fibers are depositable on the perforated band,    -   an application device through which a bonding agent, preferably        a latex layer is applicable to the layer structure,    -   a heating device in which bi component fibers and/or bonding        agents are activate able,    -   a roller arrangement preferably a calender through which the        layer structure is compressible and which has adjustable        pressure through which a movement and penetration of the SAP        particles deposited by the second air laid forming device into        adjacent cellulose fiber portions is facilitated.

Another embodiment provides that between two forming heads, preferablybetween a second and a third forming head for producing a respective airlaid layer a supply is provided through which at least one superabsorbent material, preferably SAP particles and/or SAP fibers can befed. A supply of this type can also be provided at another locationalong the device, additionally or alternatively.

A dosing of the SAP particles and/or SAP fibers can differ over thematerial width. There is also an option to arrange different SAPmaterials over the width of the material at different locations and alsoat identical locations in particular deposit the SAP. One embodimentprovides that SAP particles are arranged in a different manner over athickness of the material. A position control is provided for examplethrough a controlled alignment of the SAP feed. There is also an optionto perform this position control in an automated manner through sensors,image processing methods or similar. There is also an option that theSAP particles and/or SAP fibers are automatically checked in the layerfor example through detecting the SAP particles and/or SAP fibers. Thus,SAP particles and/or SAP fibers can include a detectable identifier suchas a special material, a color or another identifier. This facilitates acorrection during the ongoing manufacturing process.

One embodiment provides a device, wherein in a calender besides a firstsmooth roller and an opposite roller with protrusions which form a firstcalender gap a second smooth roller is provided which is arrangedrelative to the opposite roller so that a second roller gap is formed inthat during pass through of an absorbent structure with a liquidabsorption layer the second smooth roller comes in contact with theliquid absorption layer. The smooth and embossing rollers are heatable,thus the liquid absorption layer receives additional compression andsmoothing. In this arrangement, the liquid distribution layer of theabsorbent structure comes in contact with the protrusions of theopposite roller.

The further processing of the absorbent structures can be performedsubsequent to the layer production. The absorbent structures can also berolled up while still adhering to one another or can be renderedtransportable through a festooning unit. Further processing can then beperformed at another location. Further processing can be a coating,additional laminating with one or plural other layers, cutting inlongitudinal and transversal direction, another compressing and/orbonding, stretching and/or another step.

Components of an air laid production device and their relativeapplication can be derived from DE 10 2004 009 556 A1 regardingproduction of a fiber web made from cellulose fibers, from DE 10 2004214 53 A1 regarding a forming head and also regarding a method forproducing an air laid layer, from DE 10 2004 056 154 A1 regarding atransport device. Furthermore, DE 10 327 026 A1 relates to a method forproducing a fiber fleece using an air laid method and a fiber configuredfor the method. From DE 199 183 43 A1, an air laid method and an airlaid layer can be derived in which a bonding fiber is also used. From WO2005/080655 A1, the configuration of an air laid layer with differentadditional components and their layer arrangement and purpose can bederived. A detection of SAP and its controlled dispensing and possiblecorrection and the production of absorbent structures separated from oneanother can be derived from WO03/034963 A2.

The documents recited supra and also the documents recited as prior aretherein provide additional options how the device can be configured. Forthe disclosure of the invention these documents and also the prior artrecited therein are incorporated in their entirety by this reference.

The absorbent structure can be used in:

-   -   hygiene products such as baby diapers, female hygiene products,        incontinence products, make up wipes,    -   medical products such as operating room covers,    -   industrial products such as cover mats, wipes, and    -   food dishes for absorbing liquid.

Thus, the absorbent structure itself can form at least one exteriorsurface, preferably both exterior surfaces of a product. The absorbentstructure can be at least covered, preferably connected with anadditional layer at least on one side or at all sides.

Additional advantageous features and embodiments of the presentinvention are now described with reference to the subsequent embodimentswhich are also illustrated in more detail in the drawing figures. Thefeatures thus described are not limited to particular embodiments andcan be combined into additional embodiments with the other featuresdescribed supra, wherein these embodiments are not described in detail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1-FIG. 4 illustrate schematic cross sectional views of variousbonded absorbent structures using air laid fleeces;

FIG. 5 illustrates a schematic view of a first optional configuration ofa production device; and

FIG. 6 illustrates a schematic view of a second optional configurationof a production device.

DETAILED DESCRIPTION OF THE INVENTION

Turning to FIG. 1, therein illustrated is an absorbent structuregenerally designated by the reference numeral 1 and made from threelayers of an air laid material which are arranged above one another andwhich have been connected with one another in a subsequent calenderingprocess using heat and pressure. The layer structure includes thefollowing layers:

-   -   a liquid absorption layer 2 including cellulose and bi component        fibers,    -   a liquid storage layer 3 including cellulose fibers and first        SAP particles 5 and second SAP particles 6; and    -   a liquid distribution layer 4 including cellulose fibers.

Through the type of deposition process for the air laid layers and thetype of bonding process which is used for producing the absorbentstructure and which also in this case is an in line process, theparticular air laid layers of the liquid distribution layer 4, theliquid storage layer 3, and the liquid absorbent layer 2 within theboundary portion have not transitioned into one another, wherein thefibers of adjacent portions are separated from one another through anidentifiable boundary path. This boundary path for example can beclearly emphasized through different color differentiation of the fibersof different layers. The air laid layers are easily differentiated fromone another within the layer structure. In both outer boundary layers,for example, a stronger compression of the fibers is evident. The firstand the second SAP particles 5, 6 are arranged in the absorbentstructure in a random distribution and are glued together with thefibers at least in a point form manner. In the center portion of theabsorbent structure few small cavities are visible in which neitherfibers nor SAP particles are arranged.

FIG. 2 illustrates a layer structure which depicts another location ofthe same material according to FIG. 1 in an exemplary schematic view. Abonding point 7 is clearly visible in which a much stronger compressionof the material is provided. The air laid layers are furtherdifferentiable from one another in the layer structure in both figures.It is visible in FIG. 2 that preferably also at the two outer boundarylayers of the absorbent structure 1 experience a stronger compression ofthe fibers than the center portion.

FIG. 3 illustrates a second layer structure 8 without the differencerecited supra between the boundary portions and their respective centerportion of the absorbent structure. Singular stronger compressions butalso singular cavities are only slightly visible in the center portionsand also in the boundary portions of the absorbent structure. Thelayers, however, transition into one another and do not have a clearboundary but a mixed portion.

This tendency of standardizing the layers during the deposition- andbonding process is even more visible in FIG. 4 which also includes thematerial according to FIG. 3. The absorbent structure 8 includes analmost uniform compression of the fibers, in particular through thecompression as it has been provided in one bonding portion. Theparticular air laid layers are not visible any more. Even in portions inwhich SAP particles are arranged which can be considered as voids duringthe layer- and interconnection formation no differences are visible withrespect to a compression or arrangement of cavities. In the center tolower portion of the absorbent structure, SAP particles are arranged ina random distribution. The material essentially has an even compression.This effect can be generated when layers are used for producing anabsorbent structure which essentially include the same material andpreferably also a similar material thickness. For example, after thebonding process, the thickness of the layers that are not differentiablefrom one another anymore is essentially identical respectively. Withthis prerequisite and due to the fact that the SAP particles are morevisible in the lower portion of the absorbent structure, the SAPparticles protrude from the liquid storage layer into the liquiddistribution layer. This can also be identified through coloration.

Furthermore the option can be derived from FIG. 4 that a mixing zone canbe provided. This mixing zone is indicated by a dashed line which isindicated as a center line between two layers, wherein the fibers of onelayer mix with the fibers of the other layer in the sections which areemphasized by lines extending perpendicular to the center line.

FIG. 5 illustrates a schematic view of an optional configuration of adevice 9 for producing an absorbent structure including three air laidlayers. The device 9 is illustrated as an in line process with a first,a second and a third air laid forming device 10, 11, 12. It is alsoillustrated in an exemplary manner that an air laid layer isprefabricated. A roll off calender 13 on the other hand is illustratedin dashed lines. Also two or all air laid layers can be prefabricatedand only subsequently joined. Between the first and second air laidforming device 10, 11 for example a first feed 14 can be arranged. Thefeed 14 is indicated in dashed lines. Through the feed 14 for exampleSAP material or a bonding material can be fed preferably between two airlaid layers. For example, the second air laid forming device 11 mixes afirst and a second material 15, 16 with one another before the mix ofboth materials 15, 16 is also deposited on the perforated band. A mix ofthis type can for example facilitate mixes of cellulose fibers withbonding fibers, cellulose fibers with SAP fibers and/or particles andalso other combinations. A mixture of this type is not only facilitatedthrough the second air laid forming device 11. Rather also the firstand/or the third air laid forming device 10, 12 can provide this type ofmixture. Between the second and the third air laid forming device 11, 12a second feed 17 is arranged. Therein, for example, the super absorbentmaterial 18 is supplied which eventually protrudes from the liquidstorage layer into the liquid distribution layer. A heating device 19can, for example, be arranged downstream of the second forming device11. Here, the heating device 19 is illustrated as a smooth rollercalendar. Also, an infra red heater, an oven section or another heatercan be provided. Thus, for example, a bonding fiber can be activated sothat the fibers of each of both layers respectively bond with oneanother. By using the smooth roller calender, a pressure can be impartedupon the intermediary material and thus a first compression can beperformed. The material supplied through the second feed 18 is thencovered by fibers which are deposited by the third air laid formingdevice 12. Subsequent thereto, a compression can again be performed, forexample, through a heated calender 20 configured as compression unit. Acompression unit, however, can also provide a compression by hydro jet.A further compression is achieved for example by using a calender withembossings 21. Thus, another surface property can be embossed onto thelayer structure, for example, a pattern, a setting of a surface that hasremained open, a compression of SAP material from one layer into thenext adjacent layer. Furthermore, components can be used in the deviceand also a basic configuration as evident from WO 00/74620 which isincorporated in its entirety by this reference.

FIG. 6 illustrates a second optional configuration of a manufacturingdevice 22. From a winder 23, a tissue 24, i.e. a wet laid fibermaterial, is provided for further processing. The tissue 24 can beprovided, for example, through a bonding agent device 25 with a bondingagent 26. The bonding agent 26 can include a bonding fiber, a sprayed onlatex application or other means configured for bonding fibers. Thebonding agent device 25 does not have to be located at this particularlocation. The bonding agent device can also be arranged downstream of anair laid depositing device 27 and a SAP supply device 28 for applyingfirst SAP when these have layered their respective materials onto thetissue 24. The bonding agent 26 can also be used to stabilize theposition of the SAP, in particular to fixate it. The bonding agent 26can also be used to change a pore size, in particular make the pore sizesmaller. Preferably, however, in spite of the bonding agent application,the portion remains air and liquid permeable. The portion can also bepartially blocked at least also for liquid. In this illustrated method,the air laid material is deposited on the tissue and compressed andconnected through subsequent calendering under heat and pressure. Forthis purpose, the calender 29 can be heated and variably adjustable withrespect to its gap dimension. After the compression of the liquiddistribution layer thus formed, an additional air laid material isdeposited through a second air laid depositing device 30. The cellulosefibers 31 are thus mixed with the second SAP 32 and jointly depositedthereafter. Before the SAP supply unit can deposit a first SAP 33directly onto the liquid distribution layer but this is not mandatory.Furthermore also the liquid distribution layer besides cellulose fiberscan also include a SAP material 34. In other words, the SAP can bedirectly mixed with the cellulose fibers and stored in the same supplyunit or SAP can be stored in separate supply units and mixed with thecellulose fibers when being laid down by the air laid depositing device27. The weight portion of first and second SAP together is higher thanthe total weight portion of the SAP material 34. Through the movementduring the production process in particular through a vibrating machine35 which for example directly impacts the running band causing amigration of SAP into the liquid distribution layer. Thus, the vibrationmachine 35 can induce the migration with an adjustable frequency that isadapted to the band velocity. A vibration and migration thus induced canalso be caused through a movement in the production device itself, forexample through a consciously non dampened forwarding of vibrations.Thus, for example, the band movement can be utilized in a controlledmanner in order to initiate a migration of the SAP. The tissue 24preferably has a pore size that is smaller than the SAP size. Therefore,when SAP migrates into the liquid distribution layer or may already beprovided there itself, the tissue 24 prevents an exit of the SAP fromthe perforated band on which the layers are transported. A liquidabsorption layer 36 is spooled off from a winder 37 in a prefabricatedmanner and fed. Preferably, the liquid absorption layer includes thermoplastic fibers. Another calender 38 compresses and connects the layersfurther with one another through pressure and temperature. An embossing,in particular, an arrangement of heightened bonding portions orprotrusions on one of the rollers of the calender is preferably providedon the side oriented towards the liquid distribution layer. An oppositepreferred smooth roller, however, is preferably oriented towards theliquid absorption layer 36. Through the calendering, another movement orpenetration of SAP from the liquid storage layer into the liquiddistribution layer can be provided. Another treatment of the absorbentstructure 39 thus formed can be provided directly thereafter, a throughcutting unit 40 which preferably separates the particular absorbentstructures in longitudinal and transversal direction, wherein theabsorbent structures are connected with one another and distributed overthe width, or the cutting unit renders the particular absorbentstructures transportable, for example through a festooning unit 41. Theproduction device can also provide other materials besides SAP into themix. Such materials could include odor influencing materials,hydrophilic or hydrophobic embodiments and also colors, indicators,flame inhibitors, foils or similar. Also, a production of absorbentstructures can be provided as apparent for example from WO95/03019A1 orWO 03/000163 A1 which are incorporated by this reference in theirentirety, but in particular with respect to the strip shape and thecutting.

What is claimed is:
 1. A method for producing an absorbent structure,comprising at least the following steps: depositing a first layer forconfiguring a liquid absorption layer which includes at least cellulose;depositing a second layer which is air laid for configuring a liquidstorage layer which includes at least cellulose fibers and superabsorbent polymer chosen from the group consisting of super absorbentpolymer particles and super absorbent polymer fibers; depositing a thirdlayer which is air laid for forming a liquid distribution layer; movingat least one of the first, second and third layers through a heatingdevice in order to bond the same; supplying at least one of the first,second and third layers to a calender including at least one smoothroller and an opposite roller which form a calender gap; and compressingthe at least one of the first, second and third layers within thecalender gap, whereby the super absorbent polymer protrudes from theliquid storage layer into the liquid distribution layer and forms aliquid removing contact between the liquid storage layer and the liquiddistribution layer, wherein more than 20% of the super absorbent polymerarranged in the liquid storage layer protrudes into the liquiddistribution layer.
 2. The method according to claim 1, wherein thefirst layer is an air laid layer which includes cellulose fibers and bicomponent fibers.
 3. The method according to claim 1, wherein the firstlayer is air laid layer which includes a highly voluminous fleece layerfrom thermoplastic fibers.
 4. The method according to claim 1, furtherincluding the step of applying a bonding agent layer on at least one ofthe first, second and third layers.
 5. The method according to claim 4,wherein the bonding agent layer is a latex layer.
 6. The methodaccording to claim 1, wherein, in the supplying step, the first, secondand third layers are supplied to the calender gap and, in thecompressing step, the first, second and third layers are compressed inthe calender gap.
 7. The method according to claim 1, wherein theopposite roller has protrusions.